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Electroencephalogram (EEG). Doctor with a woman patient prior to an EEG examination. An EEG records the electrical activity of the brain through differences in readings from electrodes attached to the scalp. The results are either printed out onto a moving strip of paper, or they are computed and averaged. They appear as characteristic waveforms, some of which may be indicative of diseases such as epilepsy, dementia, drug disturbances and state of sleep.